Light behavior is not correct
The light behaviour is working as it should. Your mesh isn't...

You have been playing with the normals of your object, and they are all wrong. They should be perpendicular to each face, but instead they are tangents to the faces.
This was probably something you did in python since there's no interface to do it in the UI.

For a quick fix:

Properties Editor> Object Data> Geometry Data> Clear Custom Split Normals Data

I advise you to review your python code to avoid future situations like this one.